1. Field of the Invention
The present invention relates to a handover method in a wireless communications system, and more particularly, to a handover method for deciding the execution of a hand-over in consideration of portability of mobile terminal which is moving with a high speed, and an apparatus thereof.
2. Description of the Related Art
A wireless communication technology is continuously being developed to enhance data rate and to support rapid mobility. Presently, the wireless communications technology approached a level of supporting data rate adequate enough to support wireless internet despite of problems associated with noise and fading. Wireless communications systems use different method due to different standardization, and such wireless communications technologies have both merits and demerits. For example, when cellular method and Wireless Local Area Network (WLAN) method are compared, the cellular method has a broader service coverage and high mobility support for mobile terminal while having relatively lower data rate than wireless LAN method. Meanwhile, the wireless LAN method has a higher data rate while having a narrower service coverage and lower mobility support for mobile terminal than the cellular communications method.
Thus, recently, mobile terminals of multi-mode that supports a wireless communications technology of different methods are developed. A handover between wireless communications technologies with different methods is supported such multi-mode terminal. The handover which is generated in the movement between cells formed by a base station having the same communications method is called horizontal handover. On the other hand, the handover which is generated between different networks in the environment in which various different networks exist is called vertical handover. Recently, various vertical handover techniques for providing continuous handover between different networks are developed and proposed. Accordingly, in deciding a handover for a mobile terminal, an improved method different from the existing method is needed to better service the users.